1. Field of the Invention
The present invention relates to a laser welding method for welding a fiber filter to a resin base member by a laser beam.
2. Description of Related Art
Some of conventional methods for welding a nonwoven filter made of fibers to a base member made of resin are disclosed in, for example, Japanese patent unexamined publications No. Hei 8-229312 and No. 2000-186635. These welding methods include a first step of placing a nonwoven filter made of polyester fibers onto a base member made of nylon (trade name), a second step of partially melting the base member, thereby allowing the melted material to permeate through the gaps between the fibers constituting the filter to weld the filter to the base member.
Each related art mentioned above adopts an ultrasonic welding method or a vibrational friction welding method. For instance, in the ultrasonic welding method, an ultrasonic oscillator is disposed near a filter and caused to emit ultrasonic waves to melt a base member, so that the melted material of the base member permeates through the gaps between fibers of the filter and cured therein. Likewise, in the friction welding method, an oscillator is disposed near a filter. It therefore can be said that the friction welding method includes similar steps to those in the ultrasonic welding method.
The conventional welding methods, however, need a step of moving the oscillator or others toward or away from the filter. It would take some time by just that much to complete welding.
In this regard, there is a laser welding method using a laser beam as the method which can eliminate the need for moving the oscillator or other devices toward a work or reduce a moving distance of the devices. In this welding method, even where a laser emission device is placed apart from a work to be irradiated, the laser beam can reach a welding portion of the work if only the laser emission device is operated to emit a laser beam to the welding portion. If this welding method is used to weld a filter to a base member, consequently, it would be possible to omit or reduce a moving time of the emission device, thereby shortening the time required for the completion of welding.
However, there is no conventional example heretofore proposed for welding a filter to a base member by use of a laser beam. It is also conceivable that the welding by the laser beam will cause problems in securing welding strength or in preventing defects such as scorches or holes in the work. Consequentially, the proposal of a practical laser welding method has been desired.